The invention relates to a catamaran-type marine craft comprising two floats arranged spaced apart and parallel to one another which extend in the direction of travel and which are connected together at the top by a connection structure which carries built-in structures and which is sealed at the bottom by a transverse deck. The invention can fundamentally also be used with multiple hulled marine craft with more than two floats.
In particular the invention relates to a catamaran-type air cushion craft comprising two floats arranged spaced apart parallel to one another which extend in the direction of travel, with the cross-section of the floats broadening from the bottom to the top and with the floats being connected together at the top by a deck structure; resilient skirts arranged at the stem and at the stern between the floats, with the skirts extending at least approximately to the water surface and bounding, together with the floats, an inert chamber between the base of the deck structure and the surface of the water; main propulsion units which drive thrust means disposed in the stern region of the floats; and fans which blow air sucked from the outside into the bounded air chamber beneath the floor of the deck structure to lift the marine craft from travel in the displacement mode to travel in the air cushion mode.
Such marine craft are particularly suited for air cushion operation because the floats or catamaran hulls, which are still somewhat submerged during travel in the air cushion mode, represent a trouble-free sealed lateral boundary of the air chamber for the air cushion, so that resilient skirts only need to be arranged at the stem and at the stern between the floats to additionally bound the relevant air chamber towards the stem and the stern.
The disadvantage of such known catamaran air cushion craft (Naval Engineers Journal, May 1984, pages 77 to 93) is the fact that they are primarily laid out for ideal air cushion operation whereas travel in the displacement mode represents, in the final resort, an undesired state of travel adopted for example only during manoeuvring in harbour, on failure of the air cushion drive or in heavy seas, and which is only provided because it cannot be avoided in the cited circumstances.
In a known catamaran-type air cushion craft the floats have a significantly broadened hull section, which is in particular broadened out in step-like manner and which extends along a substantial fraction of their total length, substantially above the displacement float region which is submersed during travel in the displacement mode. The significantly broadened hull section serves to accommodate the main propulsion units, with the deck structure being attached to the top end region of the broadened hull sections. In this way it is ensured that trouble in the displacement mode is a state of travel of equal value to travel in the air cushion mode in which ideal conditions are present both from the point of view of economy and from the point of view of stability and travel comfort. An ideal behaviour of a catamaran-type air cushion marine craft also in the displacement mode of travel is of particular significance when the marine craft is used as a warship, because the sinking of the marine craft from travel in the air cushion mode into the displacement mode makes it more difficult to locate from a distance.
The present invention now seeks to provide a catamaran-type marine craft which has a particularly stable connecting structure which is stiff against all the forces which occur due to movement of the sea, in particular bending and torsional forces, and which, in addition to its function as a basic stabilising body for the entire marine craft, also makes it possible to carry all the important built-in structures of the marine craft which are not accommodated in the floats, which are in particular especially broad at the top, in a simple but nevertheless reliable manner.
The marine craft of the invention should be extremely economical to manufacture, to operate, to convert and to repair, should require only a small crew, should have good seagoing ability and should also be able to stay for a relatively long time at sea. The range should at least correspond to medium requirements. A broad speed spectrum with a large variation in displacement should also be ensured. The draft of the marine craft should be average to small. The invention is in particular intended for catamaran-type marine craft up to a displacement of approximately 600 tons.
In order to satisfy this object the invention provides that the connection structure includes at least two double transverse trussed girders arranged spaced apart behind one another which contain, at least in part, transverse hollow cavities for passageways and line accommodating hollow cavities, with containers and longitudinal passage and supply elements being bounted at the front and/or rear sides of the double transversed trussed girders.
The thought underlying the invention is thus to be seen in the fact that the two floats are not as it were stably connected with one another by complete deck structures but instead by quite special double transverse trussed girders which however, apart from the function of accommodating all the forces which occur at and between the floats, also have hollow cavities for transverse passageways and take on a further function in that they carry the containers and longitudinal passage and supply elements which are suspended between them.
Under a double transverse trussed girder in the sense of the invention a trussed girder should be understood which consists of two single transverse trussed girders arranged at a small distance in the longitudinal direction of the ship and rigidly connected together, with the width and the height of the double transverse trussed girders being such that a transverse passage appropriate to the size of average people can be arranged in the interior. This double construction results, on the one hand, in excellent stability of the marine craft against bending and twisting forces and provides, on the other hand, a hollow cavity extending in the transverse direction in which it is possible to accommodate not only passageways through which people can walk but also hollow cavities for the laying of lines which must be laid between the two floats, or also lead from the floats or containers to the bridge or to other units within the marine craft.
Because of the high bending and torsional stiffness of the double transverse trussed beams it is sufficient, in accordance with a particular preferred embodiment, for the connecting structure to include single transverse trussed beams arranged between at least some of the double transverse trussed beams. As the single transverse trussed beams are lighter and less complicated to manufacture it is possible in this way to manufacture a very stable ship's hull with reduced weight and cost.
It is particularly advantageous if a double transverse trussed girder and a single transverse trussed girder are arranged alternately in the longitudinal direction between the floats.
For the economical manufacture of air cushion craft in accordance with the invention it is expedient if the longitudinal spacings between sequential transverse trussed girders are made the same. In this way standardised containers can be arranged at any desired positions between the transverse trussed girders and can, if necessary, also be interchanged. This embodiment thus enables in particular the economical manufacture of series ships with a modular construction.
The construction is preferably such that the containers and the longitudinal passage and supply elements are mounted at the front and rear sides in each case to a transverse trussed girder. All the container and longitudinal passage and supply elements are thus suspended, in accordance with the invention, at the connection structure at only two sides which is useful for economical installation and removal and which considerably reduces the cost and effort of securing these components.
More economical installation and removal is also served by a further embodiment which is characterised in that the containers and the longitudinal passage and supply elements are insertable from at least one side in the transverse direction into their position between two transverse trussed girders. In this manner the ship's hull consisting of the floats and transverse trussed girders can be completed as a crude structure while the containers and the passage elements are manufactured in parallel at other places of manufacture. After the basic hull of the ship has been completed then, in accordance with the present preferred embodiment, all the built-in structures can be introduced and installed into the basic ship's hull in the shortest possible time.
It is expedient for good bending stiffness and connection stiffness for each transverse trussed girder to have a top chord, a bottom chord and trusses or struts arranged therebetween. In order to provide the required passageways in the longitudinal direction of the ship and to simultaneously ensure good stability each transverse trussed girder should have, in accordance with a further preferred embodiment of the invention, trussed sections and passage sections.
In order to be able to exploit the entire height between the top and bottom chords for the arrangement of passages which can be walked through, line carrying passages are expediently provided in the top and/or bottom chords so that the lines can be laid between the top and bottom chords outside of the intermediate space.
As already mentioned the double transverse trussed girders are expediently assembled from two single transverse trussed girders which are spaced apart in the longitudinal direction of the ship. In this arrangement the single transverse trussed girders are preferably identical with the single transverse trussed girders which are arranged between each double transverse trussed girder. This makes economical manufacture of both the single and double transverse trussed girders possible.
In order to realise torsionally stiff double transverse trussed girders, which can however be walked through, longitudinal connectors are provided at transverse intervals at the top and at the bottom between the single transverse trussed girders which jointly form the double transverse trussed girder.
Furthermore, the invention envisages, for the provision of a particularly torsionally stiff basic ship's hull, that sequential transverse trussed girders are rigidly connected together by longitudinal girders or beams. The longitudinal girders are in this arrangement expediently arranged in each case only at the top and at the bottom in such a way that the containers and longitudinal passage and supply elements can be inserted between them from the side. In this manner the longitudinal girders can also be fixedly installed before the built-in structures are introduced. A basic ship's hull which resists all loadings due to sea motion is thus realised in this way before any passage elements or containers are introduced.
In order to improve the stability of the basic hull removable vertical support are arranged, in accordance with a further embodiment, between the upper and lower longitudinal girders at the sides. The installation and removal of the passage elements and containers from the side is made possible by the removability of the vertical supports.
In an air cushion marine craft the lowermost deck which merely serves for sealing is also made air- and gas-tight.
Although intermediate decks and longitudinal transverse walls could fundamentally be built into the marine craft of the invention, it is however preferred, and an important feature of the invention, for no form of decks to be provided in the connection structure other than the lowermost transverse deck which merely serves for sealing, in particular air-sealing, and eventually intermediate floors arranged at only quite specific positions between the containers and the longitudinal passage and supply elements, and/or for no form of longitudinal walls and/or transverse bulkheads to be provided in the connection structure, other than eventually at certain specific positions between the containers and the longitudinal passage and supply elements.
The basic hull thus in practice represents a fundamental skeleton which is stable in every manner into which the containers, passage and pipe elements are suspended preferably damped against oscillation and shock.
The connection structure is preferably sealed off in water-tight manner at the sides, at the stem and at the stern by panels. The mentioned basic skeleton is thus permeable in the interior in the transverse longitudinal and vertical directions and is merely sealed off at the outer surfaces by the panels and also at the top and bottom by transverse decks.
An advantageous further development of this embodiment is characterised in that the side panels are so subdivided that they can be removed sectionwise for the introduction or removal of the containers and the longitudinal passage and supply elements from the side.
The catamaran-type marine craft of the invention is preferably so constructed that the floats have an inwardly directed projection in the upper region on which the transverse trussed girders and the lowermost deck are braced only right at the top.
This arrangement should in particular be so contrived that the projection is, at a maximum, approximately equally as wide or slightly less wide than the broadest part of the float which lies beneath it.
This embodiment is of particular significance because a relatively large width is available here for the connection of the transverse trussed beams with, in particular, the transverse bulkheads of the floats or hulls, which is of assistance for the stability of the whole ship's hull. In particular the free space between the floats which still has to be bridged by the transverse trussed beams is considerably reduced by this construction.
A preferred dimensional rule for achieving a particularly good connection and stability is characterised in that the projection is at a maximum approximately just as wide as or somewhat less wide than the broadest position of the part of the float lying beneath it. In order to accommodate as large a part as possible of the forces which occur between the floats in the region above the floats at least one trussed section and one longitudinal passage section are provided, in accordance with a preferred embodiment of the invention, at the side vertically above the associated float.
A particularly favourable ratio between the width of the support surface on the floats and the space between the floats then exists when from 40 to 55%, in particular 45 to 50% of the length of each transverse trussed girder is arranged in the region above the intermediate space between the floats, with the rest vertically above the floats.
If the marine craft of the invention is to have a higher superstructure then upper, double or single transverse trussed girders can, in accordance with a particularly preferred embodiment, be mounted on the transverse trussed girders and be of similar design but however shorter.
In this arrangement the invention expediently provides that the shorter, upper, double and single transverse trussed girders are still so long that they extend into the region vertically above the floats. The upper transverse trussed girders are thus supported in their end regions vertically on the floats via the transverse trussed girders which lie beneath them, which serves for the transmission of forces in a manner which does not load the individual components and welded connections to too great a degree.
Transverse running rails for the running in and running out, and optionally for the securing of the containers and/or the longitudinal passage and supply elements are, in accordance with a further embodiment, provided at the front and/or stern sides of the transverse trussed girders for the simple introduction of the containers and other elements from the side.
In connection with this embodiment the containers and/or the longitudinal passage and supply elements should be provided with liftable and lowerable running rollers for the associated transverse rails.
Although simple catwalks could fundamentally be installed in the double transverse trussed girders, so that they can be walked through it is however preferred for the double transverse trussed girders to contain transverse passageways which are preferably closed on all sides. In other words tube-like passageways which can be walked through and which are closed on all sides are built-into the double transverse trussed girders.
In order to obtain problemfree transitions between transverse and longitudinal passages at the desired positions longitudinal passageway connections are arranged, in accordance with a preferred further development of the invention, at the transverse passageways in the region of the longitudinal passage sections. With this arrangement longitudinal passageways are expediently attached to the longitudinal passageway connections.
In order to obtain access to containers which are capable of being walked through from the individual passageways, openings to adjoining containers should, in accordance with a preferred embodiment of the invention, branch off from the transverse passageways and/or from the longitudinal passageways.
The container openings are expediently constructed as passage elements. In particular, these passage elements should be resiliently constructed or arranged to ensure the required play for movement.
While the horizontal communication paths are formed in or between the transverse trussed girders, vertical communication paths are provided, in accordance with a preferred further development of the invention, between containers which are arranged above one another and which for this purpose preferably have appropriate openings at the top or at the bottom through which for example ladders or stairways can be passed.
It is of particularly significance in connection with the present invention, for the containers, the transverse passageways and the longitudinal passageways to be resiliently suspended on the transverse trussed girders. The construction of a marine craft in accordance with the invention is particularly suited for such resilient suspension because all chambers through which people can walk or which are taken up by shock-sensitive apparatus and systems must in any case be suspended from the rigid basic structure. For the purpose of resilient suspension it is only necessary for shock dampers to be incorporated in the suspension elements in order to ensure the desired shock damping throughout.
In order to provide a ship's superstructure of modular construction the containers and the longitudinal passage and supply elements expediently have a unit dimension corresponding to the spacing of the transverse trussed girders. Furthermore, it is expedient for the containers to have the standardised dimension or an integral multiple of this standardised dimension in the sideways direction. With this arrangement provision can in particular be made for the containers to be provided with one, two and three times the unit dimension.
The invention will now be described in the following by way of example with reference to the drawings which show: